1. Field
The present application relates to a launch control system for hybrid electric vehicles which maximizes vehicle acceleration from a standing start.
2. Description of the Related Art
Sometimes drivers like to launch their vehicles from a standing start. That is, the vehicle's engine is revved to a high speed while minimal torque is applied to the wheels. In conventional vehicles, this maneuver requires applying the brakes while revving the engine in order to hold the vehicle in place while the engine is revved. When the brakes are released, the torque is transferred through a torque converter or clutch to the wheels. Some conventional vehicles have launch control features which assists in performing this maneuver. However, hybrid vehicles cannot utilize the launch control features available in conventional vehicles.
Unlike conventional vehicles, some hybrid vehicles do not use a torque converter or clutch. Rather, these hybrid vehicles employ an electrically controlled variable transmission (ECVT). The ECVT utilizes a planetary gear, motor-generators, and control circuitry to adjust the spin rate of the engine. This allows the ECVT to control the engine speed independent of the vehicle speed. The control logic can provide a counter torque at the wheels to balance out the engine torque. The engine can be revved up while minimizing torque applied to the wheels. Although current hybrid vehicles may allow the engine to rev while keeping the vehicle at a standstill, this feature notifies the driver that the accelerator pedal is pressed and is not configured to launch the vehicle. Other hybrid vehicles may prevent the engine from revving when both the accelerator and brake pedals are applied, as a safety feature. Certain other hybrid vehicles may instead charge the battery when the brake and accelerator pedals are applied concurrently. The control logic, which further includes basic slip control logic, is designed for stability control and traction control. However, there are no launch control features in hybrid vehicles.
Thus, there is a need for a launch control system for hybrid vehicles.